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Density functional theory calculations on tilt grain boundaries in graphene

Perera, Delwin (2015):
Density functional theory calculations on tilt grain boundaries in graphene.
Darmstadt, TU Darmstadt, [Bachelor Thesis]

Abstract

The interest in graphene among researchers has not ceased since Novoselov and Geim published their findings on the electronic properties of graphene in 2004, which was acknowledged with the 2010 Nobel Prize in physics. Many aspects of graphene — electronic, magnetic or mechanic — are not completely understood. Moreover, there are many efforts to develop graphene production methods on large scales for industrial purposes. This can significantly alter graphene’s properties leading to many new problems. In industrial scale graphene production defects such as polycrystallinity are inevitable. There are few studies dealing with the change in behaviour of non-ideal graphene. In this thesis we focus on the piezoresistive properties of non-ideal graphene — i.e. graphene with grain boundaries (GB). We use interatomic potentials and density functional theory to investigate the atomic and electronic structure of different GBs. We find that multiple structures can be obtained from the same tilt angle and we arrange them according to their formation energy. To investigate the piezoresistive properties of non-ideal graphene we compute the density of states and electronic transmission functions applying different compressive and tensile strains. We show that the pentagon-heptagon-ring in Summe7 GBs possesses the lowest formation energy. Further investigation of this GB showed that electric conduction occurs in the compressive regime whereas in the tensile regime virtually no conductance is measured. This behaviour is supported by the atomic density of states where we compare the density of states contribution from GB atoms and bulk atoms. Our results confirm that GBs in graphene play a major role in the electronic transport and that they can be exploited to use graphene as a transparent strain sensor in modern electronics.

Item Type: Bachelor Thesis
Erschienen: 2015
Creators: Perera, Delwin
Title: Density functional theory calculations on tilt grain boundaries in graphene
Language: English
Abstract:

The interest in graphene among researchers has not ceased since Novoselov and Geim published their findings on the electronic properties of graphene in 2004, which was acknowledged with the 2010 Nobel Prize in physics. Many aspects of graphene — electronic, magnetic or mechanic — are not completely understood. Moreover, there are many efforts to develop graphene production methods on large scales for industrial purposes. This can significantly alter graphene’s properties leading to many new problems. In industrial scale graphene production defects such as polycrystallinity are inevitable. There are few studies dealing with the change in behaviour of non-ideal graphene. In this thesis we focus on the piezoresistive properties of non-ideal graphene — i.e. graphene with grain boundaries (GB). We use interatomic potentials and density functional theory to investigate the atomic and electronic structure of different GBs. We find that multiple structures can be obtained from the same tilt angle and we arrange them according to their formation energy. To investigate the piezoresistive properties of non-ideal graphene we compute the density of states and electronic transmission functions applying different compressive and tensile strains. We show that the pentagon-heptagon-ring in Summe7 GBs possesses the lowest formation energy. Further investigation of this GB showed that electric conduction occurs in the compressive regime whereas in the tensile regime virtually no conductance is measured. This behaviour is supported by the atomic density of states where we compare the density of states contribution from GB atoms and bulk atoms. Our results confirm that GBs in graphene play a major role in the electronic transport and that they can be exploited to use graphene as a transparent strain sensor in modern electronics.

Place of Publication: Darmstadt
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Materials Modelling
Zentrale Einrichtungen > University IT-Service and Computing Centre (HRZ) > Hochleistungsrechner
Zentrale Einrichtungen > University IT-Service and Computing Centre (HRZ)
Zentrale Einrichtungen
Date Deposited: 15 Apr 2016 11:21
Referees: Albe, Prof. Dr. Karsten and Krupke, Prof. Dr. Ralph
Refereed / Verteidigung / mdl. Prüfung: 30 July 2015
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